This operation creates an impairment of nutrient absorption as the primary factor in weight loss. This is done by removing about 2/3 of the stomach, and arranging the small intestine so that the section where food mixes with digestive juices is fairly short.

This procedure has two components. A limited gastrectomy results in reduction of oral intake, inducing weight loss, especially during the first postoperative year. The second component of the operation, construction of a long limb Roux-en-Y anastomosis with a short common "alimentary" channel of 50 cms length. This creates a significant malabsorptive component which acts to maintain weight loss long term.

Weight loss in obese patients after BPD is mainly due to lipid malabsorbtion.

Recently published long term results of this operation are reporting 72% excess body weight loss maintained for 18 years.

From the patient's perspective, the great advantages of this operation are the ability to eat large quantities of food (daily total quantity) and still achieve excellent, long term weight loss results.

Disadvantages of the procedure (BPD) are the association with loose stools, stomal ulcers, and foul smelling stools and flatus. The most serious potential complication is protein malnutrition, which is associated with hypoalbuminemia, anemia, edema, asthenia, alopecia, generally requires hospitalization and 2 - 3 weeks hyperalimentation. BPD patients need to take supplemental calcium and vitamins, particularly Vitamin D, lifelong. Because of this potential for significant complications, BPD patients require lifelong follow-up.

BilioPancreatic Diversion with Duodenal Switch

a combination of BPD and the duodenal switch, developed a hybrid operation with the advantages of the BPD but without some of the associated problems.

The procedure is a combination restrictive-malabsorptive procedure as well,

The duodenal switch consists of a suprapapillary Roux-en-Y duodeno-jejunostomy. This allows the first portion of the duodenum to remain in the alimentary stream thus reducing the incidence of stomal ulcer. When combined with a 70%-80% greater curvature gastrectomy continuity of the gastric lesser curve is maintained while simultaneously reducing stomach volume. A long limb Roux-en-Y is then created. The efferent limb acts to decrease overall caloric absorption and the long biliopancreatic limb diverting bile from the alimentary contents, specifically to induce fat malabsorption.

the main mechanism of weight loss and maintenance is malabsoprtion, with restriction playing a much lesser role.

Only the downstream 40% of small intestines is used to absorb food in this procedure, and only about one third of this is able to absorb fats and starches. The remainder of the small intestine carries the digestive juices from the liver and pancreas (the biliopancreatic flow), and as previously noted, only to the last 100cm (approx 3 feet) of food-carrying intestine. It is the 60% shortening of the intestine that initiates the weight loss and the diversion of the biliopancreatic flow which maintains that loss long-term. The stomach volume is reduced by approximately 75%, to act as a temporary restrictive effect short-term, and, more importantly, to prevent ulcers from forming long term. With the duodenal switch mechanism, the natural emptying mechanism of the stomach is preserved, eliminating the "dumping syndrome" and resulting in essentially normal eating abilities 6 months after surgery in most patients. The re-arrangement of the small intestine allows patients to eat normal volumes of food because an absorption threshold for fat and starches is established due to the biliopancreatic diversion which cannot be overeaten. The excess non-digested food is passed in the stool.

This technique was published in a paper by Marceau, Biron et al in 1993 is known as Biliopancreatic Diversion with Duodenal Switch (BPDDS). This procedure is claimed to essentially eliminate stomal ulcer and dumping syndrome.